FORTRAN Compiler using Flex/Bison

Welcome to the FORTRAN Compiler project! This project demonstrates how to build a simple, working compiler for a subset of the FORTRAN programming language using Flex (for lexical analysis) and Bison (for syntax analysis). The goal of this project is to provide an educational resource for those interested in compiler construction, particularly in using Flex and Bison for tokenization and parsing.

Table of Contents

• Introduction
• Features
• Installation
• Usage
• File Structure
• Contributing
• License

Introduction

This project serves as a simple example of how to build a compiler for a subset of the FORTRAN programming language. It focuses on the basic components of a compiler:

• Lexical Analysis (using Flex)
• Syntax Analysis (using Bison)
• Basic Error Handling

The compiler supports a limited subset of FORTRAN constructs and syntax, which can be extended to handle more complex features in the future.

Features

• Lexical Analysis with Flex: Breaks input FORTRAN source code into tokens, such as keywords (PROGRAM, REAL, INTEGER, CHARACTER, LOGICAL, etc.), identifiers, constants, and operators.
• Syntax Analysis with Bison: Parses the tokens and ensures the structure of the FORTRAN code is valid according to the defined grammar.
• Supported FORTRAN Constructs:
  • PROGRAM and END PROGRAM
  • Variable declarations (e.g., REAL :: x, INTEGER :: i, CHARACTER :: str, LOGICAL :: flag)
  • Control structures such as IF, THEN, ELSE, ENDIF
  • Loop structures like DO and ENDDO
  • Subroutine calls using CALL
  • PRINT statements for output
  • Logical and relational operators (.AND., .OR., .NOT., >, <, >=, <=, ==, !=)
  • Arithmetic expressions with +, -, *, /
  • String handling with CHARACTER and STRING
  • Logical constants (.TRUE., .FALSE.)
• Error Handling: Provides informative error messages for syntax issues, such as unmatched parentheses, incorrect statement formats, or mismatched program names.

Installation

To install and set up the project, follow these steps:

1. Clone the repository:

   git clone https://github.com/AHM-ID/FORTRAN_Compiler.git
   cd FORTRAN_Compiler

2. Install Flex and Bison:

   • On Ubuntu:

     sudo apt-get install flex bison

   • On Fedora:

     sudo dnf install flex bison

   • On Arch:

     sudo pacman -S flex bison

3. Build the compiler:

   ./scripts/build.sh

Usage

Once you've built the compiler, you can use it to compile and run FORTRAN code. Here's how:

1. Write your FORTRAN code in a file, e.g., src/fortran_code.f.

2. Run the compiled program with the provided script:

   ./scripts/run.sh

3. Alternatively, you can directly run the compiled program on your FORTRAN source code:

   ./src/fortran < your_fortran_code.f

File Structure

The project contains the following key files:

• src/fortran.l: Lexical analyzer definition using Flex. Defines how to tokenize FORTRAN code.
• src/fortran.y: Syntax analyzer definition using Bison. Specifies the grammar and how to parse tokens into a valid structure.
• src/fortran_code.f: A sample FORTRAN code for testing the compiler. You can modify this or add new files to test other aspects of the compiler.
• scripts/build.sh: A script that automates the build process for the compiler.
• scripts/run.sh: A script to execute the compiler on your FORTRAN source code.

Contributing

Contributions are welcome! If you find any bugs or want to extend the compiler's features, feel free to fork the repository, make your changes, and submit a pull request.

License

This project is licensed under the MIT License.